Monitoring of two allergens, Bet v I and profilin, in dry and rehydrated birch pollen by immunogold electron microscopy and immunoblotting

Abstract

Dry and rehydrated birch pollen grains were anhydrously fixed and double immunogold-labeled for the presence of two allergens, Bet v I major allergen (17 KD) and profilin (14 KD). In dry pollen grains, both allergens are found exclusively inside the cytoplasm. In pollen grains rehydrated for 1 min, the cytoplasm is partially devoid of the two allergens, whereas the pollen wall and the germination aperture are specifically labeled. Pollen grains rehydrated for 5 min are largely free of the two allergens. In immunoblot experiments, both allergens could be detected in the aqueous supernatants of rehydrated pollen samples within 5 min. The results obtained by both methods show the high solubility of both proteins. This makes them readily available to the immune system and characterizes them as potent allergens. Moreover, the solubilization of profilin might indicate a dissociation of the profilin-actin complex at the very first stage of pollen germination, which could favor formation of the cytoskeleton and pollen tube growth.